1. Field of the Invention
present invention relates to a corneal surgery apparatus for correcting a refractive power of an eye and removing an affected portion of a cornea by ablating part of the cornea.
2. Description of Related Art
PRK (Photorefractive Keratectomy) is a surgical operation in which part of corneal tissue (a corneal stroma and the like) is ablated with a laser beam to correct a refractive error of an eye, and PTK (Phototherapeutic Keratectomy) is a surgical operation in which an affected portion of a cornea is removed. As for those two types of operations, there are three methods to ablate a corneal region intended to be removed: a one-shot irradiation method under which a laser beam of which cross-sectional shape perpendicular to an optical axis of irradiation is a large circle (a large spot) is irradiated at one shot, a slit scan method under which a laser beam of which cross-sectional shape is rectangular is irradiated to scan at least in one direction, and a spot scan method under which a laser beam of which cross-sectional shape is a small circle (a small spot) is irradiated to scan two-dimensionally.
Also, in order to change the cornea in an asymmetric shape such as irregular astigmatism to being symmetrical such as spherical or toric shapes, under the one-shot irradiation method and the slit scan method as disclosed in U.S. Pat. Nos. 6,203,539 and 5,906,608 corresponding to Japanese Patent Unexamined Publication No. HEI09(1997)-266925 and others, a laser beam, of which cross section is profiled (restricted) into a circular or rectangular small region with a circular- or rectangular-shaped aperture, is irradiated to remove an asymmetric component of the cornea.
Under the methods described above, however, diffraction occurs when the laser beam passes through the aperture and the like, and the diffraction makes an intensity distribution (energy distribution) of the laser beam approximately concave-shaped indicating that the peripheral part of the beam has stronger intensity than the central part. Then, repeated irradiation of the laser beam having this intensity distribution may end up obtaining an inaccurate result of ablation.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a corneal surgery apparatus which enables a surgical operator to accurately ablate a cornea in part.
To achieve the objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, a corneal surgery apparatus for ablating part of a cornea by irradiating a laser beam onto the cornea of a patient""s eye comprises an irradiation optical system for irradiating the laser beam emitted from a laser light source onto the cornea, an aperture, which is disposed in the irradiation optical system, profiling a cross-sectional region of the beam perpendicular to an optical axis of the irradiation into one or more small regions, and correcting means for correcting an intensity distribution of the laser beam, which is changed when the beam passes through the aperture, to a specified intensity distribution.
In another aspect of the present invention, a corneal surgery apparatus for ablating part of a cornea by irradiating a laser beam onto the cornea of a patient""s eye comprises an irradiation optical system for irradiating the laser beam emitted from a laser light source onto the cornea, an aperture, which is disposed in the irradiation optical system, profiling a cross-sectional region of the beam perpendicular to an optical axis of irradiation into one or more small regions, and an optical member correcting an intensity distribution of the laser beam, which is changed when the beam passes through the aperture, to a specified intensity distribution, the optical member attached to the aperture on a side of the cornea.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.